Issue board milestone lists
- Similar to #5784, but for milestones.
- This is a solution to the implementing the Agile workflow of having an issue (story) backlog, and being able to manage/groom that backlog, and easily move issues (stories) between different milestones (sprints/iterations). Also you would be able to prioritize them within a sprint easily too.
- Note that in this use case, the "milestones" are indeed sprints/iterations in Agile. But in the future, we want to extend milestones to also mean releases (gitlab-org&69). I.e. in GitLab currently we don't have a distinction between release vs iteration natively.